If someone could only figure out how to get those pesky embryos to actually stick once they are put in place! If the embryos "look good" enough to transplant and they "should" implant, well then WHY don't they? I am posting here the link http://www.medicalnewstoday.com/articles/123257.php to this entire article however I didn't want you to miss the simple explanation:
"Implantation relies on a set of closely coordinated events occurring between a very early stage embryo and the lining of the womb. The embryo must initially attach to and form a contact with the lining. Then cells from the embryo begin to invade the womb lining, eventually connecting with the mother's blood vessels and forming the placenta.
'The embryo and womb lining talk to each other, molecularly speaking, which allows them to interact,' explains Professor Mardon. 'When the embryo lands on the surface of the uterus wall, it triggers a cascade of signals in both the embryo and uterus. The resulting changes allow the embryo to invade the lining.'
'This invasion process has to be tightly regulated for a placenta to form correctly and hook up with the maternal blood supply,' Professor Helen J. Mardon adds.
So what I am reading here is that the embryos can be deemed "perfect" but if the uterine lining isn't up to having a "conversation" with the embryo then all bets are off. I don't believe that this is new news...just put out there in more simplistic terms....